Method of differentially opacifying glass



Patented Aug. 11, 19 42 UNITED STATES PATENT OFFICE MEiTHOD or prrrfaliimr oraomrmo Q 7 Henry 11. man, Elmira, N. Y., assignor to Corning Glass Works, Corning, N. Y., a, corporation'or New York No Drawing. Application June 10, 1941,

Serial No. 397,497

4 Claims.

This invention relates to methods of. differentially opacifying glass by heating a selected portion thereof. In my priorpatent, Number 1,778,305, is shown a method of treating a lightsource-enclosing globe composed of a thermally opacifyable glass by inserting the bottom portion of the formed globe in an opening in the *wallof a gas fired furnace. By that method only a unitormly complete or continuous portion, such as a half, of the globe could be treated and it was not possible to heat discontinuous selected parts. a

for the purpose of forming a design;

able that the salt contained in the thermal resist should not react therewith to produce enervescence and/or noxious fumes. With the above areas either of whichmay form-the background The primary object of this invention'is to form the article either as a whole or in part. v V

The thermal resist preferably comprises a relatively inertmaterial having thermal insulating properties such as infusorial earth bonded and attached to the glass by a soluble salt or other Anotherobject is to opacity an area of a glass.

' a, low heat conductivityand then heat treating recited salt bath a thermal resist containing'barium nitrate is suitable. v

After the glass article has been heated and opacity in the selected portions has been developed to the desired degree, it iscoole'd' and washed with warm water or other solvent; 'The thermalresist isthereby readily removed and the design appears as opaciiled and unopacifled of the design. Whenthe glassper se is colored through the use of the usual coloring materials, the opacifled areas will appear substantially 'white in contrast to the color of the unopaciiled I areas. I

I claim; Y a a l. The method of making a differentially opacifled glass article which comprises forming a substantially unopaciiied article from a thermally opaciflable glass, applying to selected areas of the article=a thermal resist comprising a heatin sulating materialof 'low' thermal conductivity bonded with'a soluble salt which is substantially ini'usible at, the opaciflcation temperature of the glass, heating the article at a temperature and for a time suiiicient' to opacifythe unprotected areas and washing oil? the thermal resist. e

2.. The method 0! making a diflerentially opa'ciiled glass article which comprises forming a subsoluble substance whichwill remain substantially .unfused at the temperature to be employed for. -opacifl cation. A number oisalts fulfill these requirements, for example, the bromides and chloridesoi barium, calcium and-magnesium, barium nitrate, etc. lnpreparing the "resist" the insulating material, preferably infusorial earth, is mixed with a small amount oi-the salt and sumcient water to forms. paste 'or slurry. The mixture is-applied to theportions of the glass article which are to be protected from the heat. On drying,;the salt causes cohesion of the insulating material and furnishes adhesionto the glass surncient for the purpose in view. v

"I'he'article, thus selectively coated with'the am-m1 resist may be heated by exposure to the heated interior of a furnace or kiln or by means of a molten liquid bath into which the article is dipped. Although opaciilcation oi the selectively heated portionsof'thearticle occurs at glass temperatures ofabout 550 C. to 585 0., the temperature of'the-heat source may be somewhat above this. Anexposure of about five minutes to the heat source is -generally sufllcient for 'thepur- *stantially unopacifled article from a thermally opaciflable glass, applying to selected areas of the article a thermal resist comprising iniusorial earth and a solublesalt which is substantially infusible at the opaciflcation temperature of the glass, heating. the articleat a temperature and for a time suil lcient toopacity the unprotected areas and'washing oi! the thermal resist.

3. The method of making a diflerentially opaciiied glass article which comprises forming a substantiall'y unopacified article from a thermally 1 temperature and for a'time suiilcient to opacity V f the unprotected areas and washing oil. the'therpose. When the. heat source comprises a molten; liquid bath, for example, molten sodium or potasslum nitrate or a mixture thereoi, it is preterb ifl' e 81 pplyin to selected areas of the article a thermal" resist comprising infusor-ial earth and barium nitrate, heating the article-at a mal resist.

'4. The method it making a diflerentiallycpacitled glass article whichcomprises forming a sub stantially unopaciiied article from a thermally opaciflable glass, applying to selected areas of the I article a thermal resist -comprising intusorlal earthcnd barium nitrate, dipping; the article in a bath oi molten alkali nitrate heated to atemperature of about 690C. for about fivemlnutes, and washing of! the resist. V j

g HENRY H. 'BLAU. 

